A variety of medical conditions are treatable by the implantation of tubular devices into natural body lumens. For example, it is commonplace to implant metallic stents into the coronary arteries of patients with heart disease following balloon angioplasty to minimize the risk that the arteries will undergo restenosis. Recently, commercial stents have included drug-eluting polymer coatings that are designed to further decrease the risk of restenosis. Other examples of conventional tubular medical implants include woven grafts and stent-grafts that are used to span vascular aneurysms, polymeric tubes and catheters that are used to bypass strictures in the ureter and urethra, and stents that are used in the peripheral vasculature, prostate, and esophagus.
Despite the evolution of metallic stents, they continue to have limitations such as the possibility of causing thrombosis and vascular remodeling. While biostable and biodegradable polymeric stents have been proposed to address the limitations of metallic stents, their use has been limited by a number of factors. Among these is the fact that polymeric stents are generally not as strong as their metallic counterparts, and they may undergo stress relaxation if left in a crimped delivery configuration for an extended period of time, such as during shipping and storage. In addition, many conventional stent delivery systems, particularly for self-expanding stents, grasp the stent at isolated locations or otherwise place localized stresses on the stent. For polymeric stents, this presents the possibility that the polymer becomes permanently deformed or otherwise damaged at these localized regions. Moreover, many conventional stent delivery systems do not offer satisfactory control over the movement of a stent as it is released from the delivery system.
There is a need for a delivery system that can be used to deliver polymeric tubular implants, such as stents, into a lumen of a patient without undue risk of damaging the implant during the delivery process. There is also a need for a delivery system that offers the possibility of loading the polymeric tubular implants into the delivery system by a healthcare professional just prior to implantation, thus minimizing the possibility that the implant undergo stress relaxation during shipping and/or storage in a loaded or crimped configuration. There is also a need for a delivery system that releases a tubular implant in a controlled manner.